Novel Immunoprobe Based on MOF-818 Synergizing with an Antifouling Sensing Interface to Improve Immunosensors

Sensitivity and accuracy are both of great significance for immunosensors in practical application; thus, it is an effective strategy to improve the performance of immunosensors from the above two aspects. Herein, we reported a multifunctional immunoprobe based on metal–organic framework 818 (MOF-818) that possessed dual catalytic activity to enhance the sensitivity of immunosensors. In the presence of dopamine and hydrogen peroxide, MOF-818 can accelerate the oxidative polymerization of dopamine to couple biomolecules and facilitate the formation of semiquinone radicals and hydroxyl radicals. The obtained hydroxyl radicals promoted oxidation of the electrochemical signal molecule thionine and then realized cascade amplification of current change. To achieve high precision detection, a gold-electroplated glassy carbon electrode was assembled with an antifouling material (difunctional polyethylene glycol (HS-PEG-NH2)) to form a hydration layer, which was exploited to increase hydrophilicity and minimize non-specific adsorption. Carbohydrate antigen 72-4 (CA72-4) was chosen as a target analyte to examine the performance of immunosensors with a lower limit of detection with 26.48 nU mL–1 and a linear range from 1 μU mL–1 to 10 U mL–1. The method possessed a promising prospect in practical application due to its remarkable performance in human serum detection.